The Content delivery network or the content distribution network ( CDN ) is a geographically distributed proxy server and data center network. The goal is to distribute spatially relative services to end users to provide high availability and high performance. CDN serves most of the current internet content, including web objects (text, graphics, and scripts), downloadable objects (media files, software, documents), apps (e-commerce, portals), streaming media, streaming media requests, and social networks.
CDN is a layer in the internet ecosystem. Content owners such as media companies and e-commerce vendors pay CDN operators to deliver their content to their end users. In turn, CDN pays ISPs, carriers, and network operators for hosting their servers in their data centers.
CDN is an umbrella term that encompasses different types of content delivery services: video streaming, software downloads, web and mobile content acceleration, licensed/managed CDN, transparent caching, and services to measure CDN performance, load balancing, switching and multi-CDN analytics and cloud intelligence. CDN vendors can cross into other industries such as security, with DDoS protection and web application firewall (WAF), and WAN optimization.
Video Content delivery network
Technology
CDN nodes are commonly used in multiple locations, often over several backbones. Benefits include reducing bandwidth costs, increasing page load time, or increasing global content availability. The number of nodes and servers that make up the CDN varies, depending on the architecture, some reaching thousands of nodes with tens of thousands of servers at many remote points of presence (PoPs). Others build a global network and have a small number of geographical PoPs.
The demand for content is usually algorithmically redirected to the optimal node in some way. When optimizing for performance, the best location for presenting content to users can be selected. This can be measured by selecting the location that is the least jump, the smallest number of seconds the network of the requesting client, or the highest availability in terms of server performance (both current and historical), so as to optimize delivery across the local network. When optimizing costs, the cheapest location may be chosen instead. In an optimal scenario, these two goals tend to be parallel, since the edge servers that are close to end users on the edge of the network may have an advantage in performance or cost.
Most CDN providers will provide their services through a wide range of defined and differentiated PoP, depending on the desired coverage, such as the United States, International or Global, Asia-Pacific, etc. These PoP collections may be called "edge", "edge node" or "edge network" because they will be the closest end of the CDN asset to the end user.
The CDN Edge Network grew out of its origins through further acquisitions (through purchasing, peering, or exchanging) co-location, bandwidth, and server facilities.
Maps Content delivery network
Content network engineering
The Internet is designed according to end-to-end principles. This principle makes the core network relatively simple and drives as much intelligence as possible to the network's endpoint: residents and clients. As a result, core networks are specialized, simplified, and optimized to only forward packets.
Content Delivery Network adds an end-to-end transport network by distributing smart apps that use techniques designed to optimize content delivery. This highly integrated overlay uses web caching, server load balancing, request routing, and content services. These techniques are described briefly below.
The web cache stores popular content on the server that has the greatest demand for the requested content. This shared network equipment reduces bandwidth requirements, reduces server load, and increases client response time for cached content. Web cache filled by user request (pull cache) or based on pre-loaded content distributed from the content server (push caching).
Server load balancing uses one or more techniques including service-based (global load balancing) or hardware-based, switch 4-7 switches, also known as web switches, content switches or multilayer switches to share traffic among a number of servers or web cache. Here the switch is assigned one virtual IP address. Traffic arrives at the switch then directed to one of the real web servers attached to the switch. It has the advantage of balancing loads, increasing total capacity, improving scalability, and providing increased reliability by distributing loads of failed web servers and providing server health checks.
A content cluster or service node can be established using layer 4-7 switches to balance load across multiple servers or a number of web caches in the network.
A request routing redirects a client's request to the content source that is most capable of serving the request. This may involve directing the client request to the service node closest to the client, or the most capacity. Various algorithms are used to redirect requests. These include Global Server Load Balancing, DNS-based query routing, Dynamic metafile generation, HTML rewrite, and broadcasting. Distance - selecting the nearest service node - is estimated using a variety of techniques including reactive checking, proactive probing, and connection monitoring.
CDN uses a variety of content delivery methods including, but not limited to, manual asset copy, active web cache, and global hardware load balancer.
Content services protocol
Some protocol suites are designed to provide access to various content services distributed across the content network. The Internet Content Adaptation Protocol (ICAP) was developed in the late 1990s to provide an open standard for connecting application servers. More recently defined and robust solutions are provided by the Open Pluggable Edge Services (OPES) protocol. This architecture defines an OPES service application that can reside on the OPES processor itself or run remotely on a Callout Server. Edge Side Includes or ESI is a small markup language for assembling edge-level web content. It's common for websites to generate content. Probably because of changing content such as catalogs or forums, or due to personalization. This creates a problem for the caching system. To solve this problem, a group of companies created ESI.
CDN peer-to-peer
In a peer-to-peer (P2P) content delivery network, clients provide resources and use them. This means that unlike a client-server system, content centric networks can actually work better because more users start accessing content (especially with protocols such as Bittorrent that require users to share). This property is one of the main advantages of using P2P networks as it makes setting up and running a very small fee for original content distributors.
Private CDNs
If content owners are dissatisfied with the option or cost of a commercial CDN service, they can create their own CDN. This is called a personal CDN. A personal CDN consists of POPs (point of presence) that only serve content for the owner. These POPs can be server caching, reverse proxy or application delivery controller. It can be as simple as two server caching, or large enough to serve petabyte content.
Large content distribution networks can even build and manage their own private networks to distribute copies of content across the cache locations. Such private networks are commonly used in conjunction with public networks as backup options if the private network capacity is inadequate or there is a failure leading to a decrease in capacity. Because the same content must be distributed across multiple locations, various multicasting techniques can be used to reduce bandwidth consumption. Through private networks, it has also been proposed to select multicast trees according to network load conditions to more efficiently utilize available network capacity.
CDN trends
The emergence of CDC telkom
The rapid growth of streaming video traffic utilizes large capital expenditures by broadband providers to meet this demand and to retain customers by delivering a pretty good quality of experience.
To address this, telecom service providers (TSPs) have begun rolling out their own content delivery network as a means to reduce network backbone demands and to reduce infrastructure investment.
Telco CDN Advantages
Because they have a network in which video content is transmitted, CDN Telco has advantages over traditional CDN.
They have the last mile and can send the content closer to the end user because it can be cached deep within their network. This deep caching minimizes the distance made by video data over the public Internet and transmits it more quickly and reliably.
Telco CDN also has a built-in cost advantage because traditional CDN has to lease bandwidth from them and build operator margins into their own cost model.
Moreover, by operating their own content delivery infrastructure, telecom operators have better control over the utilization of their resources. The content management operations performed by the CDN are usually applied without (or with very limited) information about the network (eg, topology, utilization, etc.) of the telecom operators used to interact or have business connections. This poses a number of challenges for telecom operators that have limited scope of action in dealing with the impact of these operations on the utilization of their resources.
In contrast, telkom-CDN deployment allows operators to implement their own content management operations, allowing them to have better control over their resource utilization and, thus, providing better service quality and better experience to their end users.
composite CDN
In June 2011, StreamingMedia.com reported that a group of TSPs had set up Carrier Exchange Operators (OCX) to connect their networks and compete more directly with large traditional CDNs such as Akamai and Limelight Networks, which have extensive PoP around the world. In this way, telecommunications companies are building a Federation CDN offering, which is more attractive to content providers willing to deliver their content to aggregated audiences from this federation.
It is likely that in the near future, other CDN telecommunication federations will be created. They will grow by enrolling new telecommunications companies that join the federation and bring their network presence and Internet subscriber base to an existing base.
edns-client-subnet EDNS0
In August 2011, a leading global consortium of Internet service providers led by Google announced the official implementation of the Internet-Draft IETF edns-client-subnet, which is intended to accurately localize DNS resolution responses. This initiative involves a number of leading DNS and CDN service providers. With the EDNS0 edns-client-subnet option, the recursive DNS server of the CDN will use the IP address of the requesting client subnet when completing DNS requests. If the CDN depends on the DNS resolver IP address instead of the client when completing DNS requests, it can be wrong in determining the location of the client if the client uses Google redirects address for their DNS resolver, which can create latency issues. Initially, the Google DNS address 8.8.8.8 is located in California, potentially far from the client's requesting location, but now Google Public DNS servers are available worldwide.
Leading content delivery service provider
Free CDN
Traditional commercial CDN
Telco CDN
A commercial CDN uses P2P for submission
Multi CDNs
In general, all Internet service providers can provide content delivery networks.
See also
References
Further reading
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Buyya, R.; Pathan, M.; Vakali, A. (2008). Content Delivery Network . Jumper. doi: 10.1007/978-3-540-77887-5_1. ISBN: 9783540778868. - Hau, T.; Burghardt, D.; Brenner, W. (2011). "Multihoming, Content Delivery Network, and Market for Internet Connectivity". Telecommunication Policy . 35 (6): 532-542. doi: 10.1016/j.telpol.2011.04.002.
- Majumdar, S.; Kulkarni, D.; Ravishankar, C. (2007). "Addressing Click Fraud in Content Delivery Systems" (PDF) . Infocom . IEEE. doi: 10.1109/INFCOM.2007.36.
- Nygren., E.; Sitaraman R. K.; Sun, J. (2010). "Akamai Network: Platform for High Performing Internet Applications" (PDF) . ACM SIGOPS Overview of Operating System . 44 (3): 2-19. doi: 10.1145/1842733.1842736 . Retrieved November 19, 2012 .
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Vakali, A.; Pallis, G. (2003). "Content Delivery Network: Status and Trends". IEEE Internet Computing . 7 (6): 68-74. doi: 10.1109/MIC.2003.1250586.
Source of the article : Wikipedia
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